Multiple sclerosis is considered to be an immune-mediated disease in which the body's immune system attacks the central nervous system. Some MS experts believe it to be an autoimmune disease, although this continues to be the subject of debate in the scientific community. The prefix “auto” means “self.” Autoimmunity means that the immune system is reacting against normally-occurring antigens in the body, as if these antigens were foreign. Antigens are generally proteins that stimulate an immune response. However, no specific antigen has yet been identified in MS, leading many MS experts to conclude that MS cannot be classified as an autoimmune disease at this time.
Some diseases thought to have an autoimmune basis are:
- myasthenia gravis
- rheumatoid arthritis
- systemic lupus erythematosis
- insulin-dependent (Type 1) diabetes mellitus.
In the case of MS, the immune system attacks the central nervous system, including myelin, the fatty sheath that surrounds and protects nerve fibers. T-cells, which are one type of white blood cell in the immune system, become sensitized to myelin and cross the blood-brain barrier into the central nervous system (CNS). Once in the CNS, these T-cells not only injure myelin, but secrete chemicals that damage nerve fibers (axons) and recruit more damaging immune cells to the site of inflammation.
It is not known what causes T-cells in persons with MS to become activated but it is postulated that both genetic and environmental factors are important.
Research Directed at Role of Immune System in MS
Scientists have begun to identify the sites or “receptors” on the T-cells that bind to the myelin. The precise identification of these receptor sites may help lead to the development of more specific immunosuppressant therapies that destroy these sensitized T-cells while leaving other cells intact. Much of the ongoing research in MS is directed toward finding answers to questions about the role of the immune system in the development of MS.